1. Field of the Invention
The present invention relates to a motor having a fluid bearing, and more particularly, to a motor having a bearing groove in a rotary shaft of a rotor (rotary body), in which a clearance control unit is formed at an external side of a housing and a shaft groove for inserting the rotor shaft to uniform an air pressure between the bearing groove on an external side of the rotor shaft and an internal side of the shaft groove.
2. Description of the Related Art
Generally, in an apparatus having a motor and a rotor in which a fluid bearing is mounted, a predetermined clearance is formed between a rotor shaft and an internal side of a shaft groove wherein the rotor shaft is inserted, when the rotor shaft rotates. The clearance occurs due to an air pressure formed in a plurality of bearing grooves on an external side of the rotor shaft when the rotor shaft rotates.
Furthermore, a predetermined clearance of several um is maintained between the internal side of the shaft groove and the external side of the rotor shaft. The air pressure occurring therebetween is susceptible to a fine change in the internal side of the shaft groove as well as the external side of the rotor shaft.
Thus, when the rotor shaft having a conventional fluid bearing rotates, the internal side of the shaft groove or the external side of the bearing groove may become rough or uneven due to unexpected external forces and the like. In this case, the position of the rotor shaft is varied with respect to the internal side of the shaft groove. As a result, oscillation of the rotor shaft occurs when the rotor shaft rotates.
Such oscillation of the rotor shaft causes malfunction of the motor and the apparatus having a rotary body such as the rotor shaft. For example, in the case of a scanning motor, if oscillation of the rotary shaft occurs, a polygon mirror oscillates, too. The polygon mirror is a polygonal plate body having a predetermined thickness and is generally made of aluminum material. The polygon mirror is mounted into a sleeve of a rotor in the scanning motor which is mounted into a scanner or a laser printer. If the rotor rotates, the polygon mirror rotates at the same time and reflects laser beams emitted from a predetermined position to deflect the laser beams into a printing drum. If oscillation of the polygon mirror occurs, the laser beams are not reflected upon the polygon mirror at an exact angle. This significantly reduces reliability of the product such as the scanner or the laser printer.